The aim of this project is to characterize the properties of voltage gated channels and synaptic transmission of hippocampal inhibitory neurons in the developing brain and how these properties impact hippocampal function under both physiological and pathological conditions. Although much is known about their neurochemistry, their role in the local circuits and the basic electrophysiological properties of inhibitory interneurons, little is known about the specific ionic or ligand gated channels expressed on this highly divergent population of cells. A major part of our effort is to understand the ionic mechanisms which regulate the activity of these cells and how these mechanisms impact hippocampal function using patch clamp, immunohistochemical and molecular techniques. Our work over the past year has focussed on particular populations of inhibitory neurons of the CA1 stratum oriens/alveus and pyramidal cell layers. Particularly we have characterized the complement of potassium channels present on these cells using both a combined electrophysiological and immunohistochemical approach. We have determined the roles of voltage-gated currents in st. oriens-alveus interneurons in determining the action potential and firing patterns of these cells. In addition we have investigated the developmental expression and functional role of the K channel 2subunit Kv3.1 in parvalbumin containing interneurons of st. pyramidale.The role of various types of interneuron during the plastic phenomena of long term depression and potentiation using perforated patch and paired reording techniques has also been studied.